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← Everything for Calculus I
Calculus IDerivatives

The chain rule, one layer at a time.

Find the inside, differentiate the outside, then multiply by the inside’s derivative. Build the idea step by step, then try every question from your notes.

Inside and outside · Step 1 of 10

A composition feeds one output into another function

x ⟶ 2x+1 ⟶ (2x+1)2{\displaystyle x\ \longrightarrow\ 2x} + {\displaystyle 1\ \longrightarrow\ (2x+1)^2}
The order of operations
f(g(x))=(2x+1)2{\displaystyle f(g(x))} = {\displaystyle (2x+1)^2}
Write the composition
A function takes an input and returns an output. In f(g(x)){f(g(x))}, g is inside: do it first. Then feed that entire result into f, the outside. This is composition, not multiplication. Here f(x)=x2{f(x)} = {x^2} and g(x)=2x+1{g(x)} = {2x+1}.
Try it: Choose the order and move the input. Predict the two outputs before revealing them.
Order
Input x1
g(1)=2(1)+1=3{\displaystyle g(1)} = {\displaystyle 2(1)} + {\displaystyle 1} = {\displaystyle 3}
First output
f(3)=(3)2=9{\displaystyle f(3)} = {\displaystyle (3)^2} = {\displaystyle 9}
Final output
Check yourself
In 1+sin⁡x{\sqrt{1+\sin x}}, what is the outermost operation?

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